The recent technical progress of a silver halide color photographic light-sensitive materials (hereinafter sometimes referred to as a `color light-sensitive material` or simply a `light-sensitive material`) has been remarkable. It is the matter of course on the one hand that the improvements of photographic characteristics such as sensitivity and image-quality have been required as heretofore, and on the other hand that every product has recently been required further to have a global environmental aptitude from the viewpoints of a resource-saving, an energy-saving and environmental issues.
For the saving of resources, a light-sensitive material has been demanded to save a coating weight of silver as much as possible, from the viewpoint for making effective use of a valuable silver resource as a raw material of silver halide grains applicable to a light-sensitive material. However, in a low silver-containing light-sensitive material, it has been difficult to save a silver content drastically, because the drastic saving thereof results in deterioration in image-qualities, particularly a graininess, and it also induces lowering of a contrast gradation and a color density, which are necessary for photographic characteristics.
Generally, when reducing an silver coating weight from a color light-sensitive material, there have been some instances where a coupler amount is increased in or a highly developable silver halide is introduced into a light-sensitive material so as to enhance a color density. Each of these measures is rather unfavorable for a processing stability of a light-sensitive material. Particularly, in such a processing system as a mini-lab that has recently been on the rise, the demands from a mini-lab for the processing stability of a light-sensitive material have been particularly getting increased more than ever, because a rapid and low-replenishing process has been the main process.
From the viewpoint of a quality control, the essential factors include not only variations in sensitivity, and image-quality produced by a processing fluctuations, but also a characteristic change produced during a period from the delivery of the light-sensitive material to the development process (so-called shelf-life). According to the studies performed by the present inventors, it has become clear that an ordinary negative type light-sensitive material for picture-taking use is hardly affected by the environmental conditions when the silver coating weight of the light-sensitive material is not less than 4.5 g/m.sup.2, but some kind of storage stabilities are seriously affected by the environmental conditions when the silver coating weight thereof is not more than 4.5 g/m.sup.2 so as to deteriorate the photographic characteristics thereof.
On the other hand, it has been well-known to spectrally sensitize a silver halide emulsion applicable to a color light-sensitive material. Most of the spectral sensitizing dyes used for the spectral sensitization are insoluble in water. It is generally known in the art to dissolve a sensitizing dye in a solvent and then to add the solution to a silver halide emulsion.
As for the solvents for a sensitizing dye, particularly, a water-miscible organic solvent has so far been used. For example, alcohol, ketone, nitrile and alkoxy alcohol have been used for. The typical examples thereof include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, ethylene glycol, propylene glycol, 1,3-propane-diol, acetone, acetonitrile, 2-methoxy-ethanol and 2-ethoxy-ethanol.
There is a widely known technique in which a surfactant is used for dissolving a sensitizing dye. Such a surfactant as mentioned above include, for example, an anionic type surfactant, a cationic type surfactant, a nonionic type surfactant and an amphoteric type surfactant.
However, when making use of a conventionally ordinary sensitizing technique is applied to a silver halide emulsion having a relatively small silver content, it is not satisfactorily cope with a shelf-life, a processing stability and so forth. Therefore, an improvement thereof has been demanded so far.
A technique for mechanically dispersing an organic dye in an aqueous medium is known in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as JP OPI Publication) No. 3-288842/1991. However, this technique is to prevent an organic dye from diffusing in a photographic light-sensitive material. It is only a dispersion-addition technique and the purpose of making use of this technique is quite different from the purpose of making a spectrally sensitizing dye adsorbed uniformly and effectively to the surfaces of silver halide grains.
Accordingly, the present inventors have variously studied on low silver coverage light-sensitive materials capable of contributing the saving of resources so as to provide a light-sensitive material excellent in shelf-life and processing stability. As the results, they have discovered that such a light-sensitive material as mentioned above can be provided by mechanically dispersing a sensitizing dye in a system having no organic solvent nor surfactant and then by adding the resulting dispersion to the light-sensitive material.